The security flaw affected all Mac devices running the latest version of High Sierra (at least version 10.13.1 - 17B48), according to a report.

Apple has reportedly apologised and rolled out an update to fix a major security flaw in its Mac operating system (OS) that lets anyone log into Mac devices running without a password. "Security is a top priority for every Apple product, and regrettably we stumbled with this release of macOS," The Telegraph quoted an Apple spokesperson as saying late Wednesday.

The latest version of MacOS will automatically download the update. "When our security engineers became aware of the issue Tuesday afternoon, we immediately began working on an update that closes the security hole. The update is available for download, and starting later today it will be automatically installed on all systems running the latest version (10.13.1) of macOS High Sierra," the tech giant added.

The security flaw affected all Mac devices running the latest version of High Sierra (at least version 10.13.1 - 17B48), according to TechCrunch. The vulnerability was discovered by Turkish developer Lemi Orhan, who found that the Mac log-in screen can be cracked simply by entering the word "root" as a username and hitting enter twice, without having to enter a password.